Diffusion transfer system comprising dye developers, a pyrazolone and an onium compound

ABSTRACT

Improved color separation is achieved in color diffusion transfer systems such as multicolor dye developer systems by processing exposed photosensitive elements in the presence of a 5-pyrazolone unsubstituted in the 4-position in combination with an onium compound.

O Umted States Patent [151 3,649,265 Stewart Mar. 14, 1972 [54]DIFFUSION TRANSFER SYSTEM [56] References Cited COMPRISING DYEDEVELOPERS, A

UNITED STATES PATENTS PYRAZOLONE AND AN ONIUM 3 2 3 2 96 B arr COMPOUND3,312,549 4/1967 Salminen ..96/29 1) [72] Inventor: Paul Harold Stewart,Rochester, NY. 3,173,786 3/ 1965 Green et al. ..96/3 [73] Assigneezfiaztman Kodak Company, Rochester, Primary Emmmer Nrman G. Torch!Assistant Examiner-Alfonso T. Suro Pico Filtid! y 1970 Attorney-W. H. J.Kline, J. R. Frederick and H. E. Cole 211 App]. No.2 35,290 [57]ABSTRACT 52 U.S. c1. ..96/3 96/29 D 96166.3 SeParation is achieved in 511m. 01 ..G03C 7/00, 003 6 5/54 G036 5/30 "ansfer Systems as dye devebp"Systems 58 1 Field Of Search ..96/3, 29 D, 66.5, 66, 66.3 Processinge'emems the Presence a S-pyrazolone unsubstituted in the 4-position incombination with an onium compound.

18 Claims, No Drawings DIFFUSION TRANSFER SYSTEM COMPRISING DYEDEVELOPERS, A PYRAZOLONE AND AN ONIUM COMPOUND This invention relates tothe art of photography and more particularly to a multicolor diffusiontransfer process in photography and materials adapted for use in theprocess.

A diffusion transfer color process has been described in a numberofpatents, including US. Pat. No. 2,983,606, wherein photographicelements containing silver halide emulsion layers and layers containingdifiusible dye developers (dyes having a silver halide developingfunction) are exposed to record the latent image in the silver halideand then treated with an alkaline processing composition which permeatesthe emulsion layers and layers containing the dye developers which thendevelop the latent images to silver images. At the same time, oxidationproducts of the dye developers are formed in situ with the silver imagesand which are relatively nondiffusing in the colloid vehicle of thelayers.

The nondiffusing character of the oxidized dye developers is apparentlydue at least in part to a decrease in solubility in the alkalineprocessing liquid, and may also be due to a hardening effect of theoxidized developer upon the colloid vehicles of the layers which retardsthe diffusion of the oxidized dye developers. The residual unoxidizeddye developers remaining in the layers in imagewise distribution aretransferred by diffusion to a superposed reception element substantiallyto the exclusion of the silver image and oxidized dye developer toprovide a positive dye image.

When an element containing differentially sensitized silver halideemulsion layers is used and substractively colored dye developers arepresent in or contiguous to the respective emulsion layers, upontreatment with the processing liquid the dye developers are oxidized andrendered nondiffusing in the developed regions of the layers and theresidual dye developer images in the positive regions are transferred bydiffusion and in register to the reception element to provide amulticolor reproduction.

It has been proposed in US. Pat. No. 3,173,786 to employ onium compoundsas development accelerators for the processing of dye developernegatives. Thus, the onium compounds coact with the dye developers toincrease the transfer of the dye developers from unexposed areas of thenegativev The onium compounds act to inhibit the transfer of the dyedevelopers from exposed areas thereby improving the highlights. Thisimprovement in highlights is apparently due, at least in part, to theability of the oniums through salt formation with'the dye developers tocontrol the diffusibility of the dye developers, especially in exposedareas.

Broadly, the proposed onium compounds include quatemary ammonium,quaternary phosphonium, and tertiary sulfonium compounds. The quaternaryammonium compounds are indicated as yielding especially useful results.Likewise, it is taught that those onium compounds which contain areactive methyl group, i.e., a methyl group which is capable of forminga methylene base in alkali, provide improved color separation. Thus, theemployment of an onium compound having a'reactive methyl group, e.g.,l-benzyl-Z-picolinium bromide, results in the transfer of the dyedeveloper being more closely controlled by the silver halide emulsionwith which each dye developer is associated. On the other hand, oniumcompounds, such as l-phenethyl pyridinium bromide, which do not formmethylene bases in alkali solutions are indicated to be less useful. Itwould be highly desirable to provide a transfer system in which oniumcompounds which do not pos sess a reactive methyl group could berendered more useful.

It is therefore an object of the invention to provide a novel colordiffusion transfer system in which good print quality can be obtainedwith onium compounds including those having no reactive methyl group.

A further object of the invention is to provide a novel process for theproduction of a multicolor diffusion transfer image having better colorseparation than heretofore obtainable employing onium compounds havingno reactive methyl group.

These and other objects are achieved in accordance with the presentinvention whereby color diffusion transfer processes are conducted inthe presence of a S-pyrazolone unsubstituted in the 4-position incombination with an onium compound.

As will be hereinafter demonstrated, it has been discovered that printshaving good color separation are obtainable with onium compoundsincluding those having no reactive methyl group, e.g., l-phenethylpyridinium bromide, when the onium compound is used in combination witha 5-pyrazolone unsubstituted in the 4-position.

In accordance with the present invention, a photographic film unit isprovided which is adapted to be processed by passing the unit between apair of juxtaposed pressure-applying members. The film unit comprises:

a. a photosensitive element comprising a support coated with at leastone photosensitive silver halide emulsion layer, each silver halideemulsion layer having associated therewith a dye image-providingmaterial;

a dye image-receiving layer; and

c. a rupturable container containing an alkaline processing composition;said film unit containing a 5-pyrazolone unsubstituted in the 4-positionand an onium compound, said rupturable container being adapted to bepositioned during processing of said film unit so that a compressiveforce applied to said container by said pressure-applying members willeffect a discharge of the container's contents within said film unit.

Development of the exposed silver halide emulsion layers of theabove-described film unit is conducted in the presence of at least oneonium compound and especially in the presence of at least one oniumcompound possessing no reactive methyl group. The onium compounds arepreferably selected from the group consisting of quaternary ammonium,quaternary phosphonium, and tertiary sulfonium compounds.

Especially useful results have been obtained through the use ofquaternary ammonium compounds. As is known, quaternary ammoniumcompounds are organic compounds containing a pentavalent nitrogen atom.Generally, they can be considered as derivatives of ammonium compoundswherein the four valences usually occupied by the hydrogen atoms areoccupied by organic radicals. Generally, the organic radicals are joineddirectly to the pentavalent nitrogen through a single or doublecarbon-to-nitrogen bond. The term quaternary ammonium, as used herein,is intended to cover compounds wherein the pentavalent nitrogen is oneof the nuclear atoms in a heterocyclic ring as well as those whereineach of the four valences is attached to separate organic radicals,e.g., tetraalkyl quaternary ammonium compounds. As illustrations ofquaternary ammonium compounds, mention may be made of those representedby the following formulae:

wherein each R is an organic radical, Y is an anion, e.g., hydroxy,bromide, chloride, toluene sulfonate, etc., and Z represents the atomsnecessary to complete a heterocyclic ring. As examples of compoundswithin Formulae l, 2, and 3, mention may be made of tetraethylammoniumbromide, N- ethylpyridinium bromide and N,N-diethylpiperidinium bromide.

The tertiary sulfonium and quaternary phosphonium compounds may berepresented by the Formulae:

(R) S X {4| and M X (5) wherein each R is an organic radical, e.g.,alkyl, aralkyl, aryl, etc. groups, and X is an anion, e.g., hydroxy,bromide. chloride, toluene sulfonate, etc. As examples of tertiarysulfonium and quaternary phosphonium compounds, mention may be made oflauryldimethylsulfonium p-toluene sulfonate, nonyl-dimethylsulfoniump-toluene sulfonate. butyldimethylsulfonium bromide, triethylsulfoniumbromide, tetraethylphosphonium bromide, etc.

The onium compounds can be used as the free base or as the salt. Whenthe onium compounds are used as the salt, the anion may be a derivativeof any acid. However, it should be noted that when the anion is iodide,such iodide may have deleterious effects on the emulsion and suitableprecautions should be taken. Especially good results are obtained whenthe onium compounds are employed as the bromide. When using oniumcompounds, which have an anion other than bromide, it has been foundadvantageous in certain instances to add a small amount of potassiumbromide. Additional onium compounds are disclosed in U.S. Pat. No.3,260,597 to Weyerts et al. the disclosure of which is herebyincorporated by reference.

Especially preferred onium compounds of the present invention are thepyridinium salts which do not form methylene bases in alkali solutionsincluding:

l-phenethyl pyridinium bromide l-ethyl pyridinium bromidel-phenethyl-3-picolinium bromide l-n-nonylpyridinium p-toluenesulfonate,and the like.

The S-pyrazolone compounds useful in the present invention aredistinguished from other pyrazolones in that the 4- position is alwaysunsubstituted, i.e., an active methylene group is always present at the4-position. This may be illustrated by the following formula:

II( 1-CR I ll /C@@N 1% wherein R is hydrogen, aryl or alkyl includingsubstituting aryl and alkyl. Examples of such compounds include1-phenyl-3- methyl-S-pyrazolone, l-p-nitrophenyl-3-methyl-5-pyrazolone,1-a-naththyl-3-methyl-5-pyrazolone, l-p-bromophenyl-3-methyl-S-pyrazolone, 1-phenyl-3-ethoxy-5-pyrazolone, 1-phenyl-3-butoxy-5-pyrazolone, l-p-nitrophenyl-Ii-ethoxy-S- pyrazolone,l(p-sulfamylphenyl)-3-ethoxy-5-pyrazolone, lphenyl-3-acetylamino-5-pyrazolone, l-phenyl-3-propionylamino-S-pyrazolone, the compounds disclosed on pages 2, 3 and 4of U.S. Pat. No. 2,369,489 of Porter et a1. issued Feb. 13, 1945, etc.

The onium compound and the S-pyrazolone unsubstituted in the 4-positioncan be provided in any suitable manner in the photographic film unit solong as they are present during development of the exposed silver halideemulsion layers of the film unit. Thus, for example, the onium and the5- pyrazolone unsubstituted in the 4-position may be present in eitheror both the alkaline processing composition, in the reception sheet orin the photosensitive element.

The concentration of the onium compound can be varied over a wide rangedepending upon particular needs. Thus, for example, between about 1 andabout percent, preferably between about 2 and about 4 percent by weightof the processing composition can comprise the onium compound. Likewise,the 5-pyrazolone unsubstituted in the 4-position can be present in anamount, for example, of between about 0.5 and about 5.0 percent,preferably between about 1 and 4.0 percent by weight of the processingcomposition.

The dye image-receiving layer of the film unit can be located on aseparate support adapted to be superposed on the photosensitive elementafier exposure thereof. Such imagereceiving elements are disclosed, forexample, in U.S. Pat. No. 3,362,819. The rupturable container is usuallypositioned during processing of said film unit so that a compressiveforce applied to the container by pressure-applying members in a camerawill effect a discharge of the containers contents between theimage-receiving element and the outermost layer of the photosensitiveelement. The dye image-receiving layer can also be located integral withthe photosensitive element between the support and the lowermostphotosensitive silver halide emulsion layer. Such integralreceiver-negative photosensitive elements are disclosed, for example, inU.S. Pat. No. 3,415,644 and useful in camera apparatus of the typedisclosed in Belgian Pat. Nos. 7l8,553 and 718.554. Another embodimentof an integral receiver-negative photosensitive element in which theinstant invention may be employed is described in U.S. Pat. No.2,983,606, column 14, lines 27-55.

The film assembly of the invention can be used to produce positiveimages in single or multicolors. in a three-color system, each silverhalide emulsion layer of the film assembly will have associatedtherewith a dye image-providing material processing a spectralabsorption range substantially complementary to the predominantsensitivity range of its associated emulsion, i.e., the blue-sensitivesilver halide emulsion layer will have a yellow dye image-providingmaterial associated therewith, the green-sensitive silver halideemulsion layer will have a magenta dye image-providing materialassociated therewith, and the red-sensitive silver halide emulsion layerwill have a cyan dye image-providing material associated therewith. Thedye image-providing material associated with each silver halide emulsionlayer may be contained either in the silver halide emulsion layer itselfor in a layer contiguous to the silver halide emulsion layer.

The various silver halide emulsion layers of the color film assembly ofthe present invention may be disposed in the usual order, i.e., theblue-sensitive silver halide emulsion layer first with respect to theexposure side followed by the green-sensitive and red-sensitive silverhalide emulsion layers. lf desired. a yellow dye layer or a Carey Leasilver layer may be present between the bluesensitive andgreen-sensitive silver halide emulsion layer for absorbing or filteringblue radiation that may be transmitted through the blue-sensitive layer.if desired, the selectively sensitized silver halide emulsion layers maybe disposed in a different order, e.g., the red-sensitive layer firstwith respect to the exposure side, followed by the green-sensitive andblue-sensitive layers.

Any dye image-providing material can be employed in the present filmunit, provided that an imagewise distribution of the material will beformed after development as a function of the imagewise exposure of thesilver halide emulsion to which the dye image-providing material isassociated. Particularly good results are obtained when the dyeimage-providing materials are dye developers, i.e., compounds whichcontain in the same molecule both the chromophoric system of a dye andalso a silver halide developing function. A preferred silver halidedeveloping moiety in such dye developers is a hydroquinonyl group. Dyedevelopers and their functioning in color diffusion transfer systems arewell known in the art as shown, for example, by U.S. Pat. Nos.2,983,606; 2,992,106; 3,047,386; 3,076,808; 3,076,820; 3,077,402;3,126,280; 3,131,061; 3,134,762; 3,134,765; 3,135,604; 3,135,605;3,135,606; 3,135,734; 3,141,772; and 3,142,565.

When dye developers are employed as the dye imageproviding materials inthe film assembly of this invention, an alkaline processing oractivating composition is conveniently employed in the rupturablecontainer or pod. After exposure of the element, the alkaline processingcomposition is released from the pod to permeate the emulsion layers andinitiate development of the latent images contained therein. The dyedevelopers are immobilized in exposed areas as a consequence of thedevelopment of the latent images. This immobilization is due at least inpart, to a change in the solubility characteristics of the dyedevelopers upon oxidation.

In unexposed areas of the emulsion layers, the due developers remaindiffusible and thus provide imagewise distributions of unoxidized dyedeveloper dissolved in the liquid processing composition as a functionof the point-to-point degree of exposure of the silver halide emulsionlayers. At least part of these imagewise distributions of unoxidized dyedeveloper are transferred, by diffusion, to the image-receiving layer.The image-receiving layer contains materials adapted to mordant orotherwise fix the diffused, unoxidized dye developers.

Good results are obtained when dye developers are employed in separatelayers contiguous to each silver halide emulsion layer. Such layers canbe applied by using coating solutions containing about 0.5 to about 8percent, by weight, of the dye developer distributed in a hydrophilicfilm-forming natural material or synthetic polymer such as gelatin,polyvinyl alcohol, etc., which is adapted to be permeated by aqueousalkaline processing composition.

In addition to conventional techniques for the direct dispersion of aparticulate solid material in a polymeric or colloidal matrix such asball-milling and the like techniques, the preparation ofa dye developerdispersion can also be obtained by dissolving the dye developer in anappropriate solvent or mixture of solvents, dispersing the resultantsolution in the polymeric binder, with optional subsequent removal ofthe solvent or solvents employed. Further details concerning thesedispersing techniques and the solvents employed are found, for example,in U.S. Pat. Nos. 2,269,158; 2,322,027; 2,304,939; 2,304,940; 2,801,171;etc.

Other dye image-providing materials which can be employed in thisinvention include coupling dyes as disclosed, for example, in U.S. Pat.No. 3,087,817, shifted or colorless dye developers as disclosed, forexample, in U.S. Pat. No. 3,230,085, dye developer-precursors,dye-precursor developers, metal-dye complexes as disclosed, for example,in U.S. Pat. No. 3,185,567 and U.S. Pat. No. 3,453,107, nondiffusiblecouplers as disclosed in U.S. Pat. Nos. 3,227,550 and 3,227,551,couplers requiring an oxidizing agent in the imagereceiving layer inorder to form colors, ring-closing dye developers as disclosed in U.S.Pat. No. 3,443,943, colorproviding materials as disclosed in U.S. Pat.Nos. 3,443,940 and 3,443,941, etc. These dye image-providing materialscan be incorporated into the photosensitive element in the same mannerlisted above for dye developers.

In a color film unit according to the present invention, each silverhalide emulsion layer containing a dye image-providing material orhaving the dye image-providing material present in a contiguous layercan be separated from the other silver halide emulsion layers in thefilm unit by materials including gelatin, calcium alginate, or any ofthose disclosed in U.S. Pat. No. 3,384,483, polymeric materials such aspolyvinylamides as disclosed in U.S. Pat. No. 3,421,892, or any of thosedisclosed in U.S. Pat. Nos. 2,992,104; 3,043,692; 3,044,873; 3,061,428;3,069,263; 3,069,264; 3,121,01 1;and 3,427,158.

Generally speaking, except where noted otherwise, the silver halideemulsion layers of the invention comprise photosensitive silver halidedispersed in gelatin and are about 0.6 to 6 microns in thickness; thedye image-providing materials are dispersed in an aqueous alkalinesolution-permeable polymeric binder, such as gelatin, as a separatelayer about 1 to 7 microns in thickness; and the alkalinesolution-permeable polymeric interlayers, e.g., gelatin, are about 1 to5 microns in thickness. Of course, these thicknesses are approximateonly and can be modified according to the product desired.

The silver halide emulsions used with this invention can comprise silverchloride, silver bromide, silver bromoiodide, silver chlorobromoiodideor mixtures thereof. The emulsions can be coarse or fine grain and canbe prepared by any of the well-known procedures, e.g., single jetemulsions, double jet emulsions, such as Lippmann emulsions, ammoniacalemulsions, thiocyanate or thioether ripened emulsions such as thosedescribed in Nietz et al. U.S. Pat. No. 2,222,264; lllingsworth U.S.Pat. No. 3,320,069; and McBride U.S. Pat. No. 3,271,157. Surface imageemulsions can be used or internal image emulsions can be used such asthose described in Davey et al. U.S. Pat. No. 2,592,250; Porter et al.U.S. Pat. No. 3,206,313 and Bacon et al. U.S. Pat. No. 3,447,927. Theemulsions may be regular grain emulsions such as the type described inKlein and Moisar, J. Phot. Sci., Vol. 12, No. 5, Sept./Oct., 1964, pp.242-251. If desired, mixtures of surface and internal image emulsionscan be used as described in Luckey et al. U.S. Pat. No. 2,996,382.Negative-type emulsions can be used or direct positive emulsions can beused such as those described in Leermakers U.S. Pat. No. 2,184,013;Kendall et al. U.S. Pat. No. 2,541,472; Berriman U.S. Pat. No.3,367,778; Schouwenaars British Pat. No. 723,019; lllingsworth et al.French Pat. No. 1,520,821; lves U.S. Pat. No. 2,563,785; Knott et al.U.S. Pat. No. 2,456,953 and Land U.S. Pat. No. 2,861,885.

The silver halide emulsions can be unwashed or washed to remove solublesalts. 1n the latter case the soluble salts may be removed bychill-setting and leaching or the emulsion may be coagulation washed,e.g., by the procedures described in Hewitson et al. U.S. Pat. No.2,618,556; Yutzy et al. U.S. Pat. No. 2,614,928; Yackel U.S. Pat. No.2,565,418; Hart et al. US. Pat. No. 3,241,969; and Waller et al. U.S.Pat. No. 2,489,341.

Also, the silver halide emulsions can contain speed-increasing compoundssuch as polyalkylene glycols, cationic surface active agents andthioethers or combinations of these as described in Piper U.S. Pat. No.2,886,437; Dann et al. U.S. Pat. No. 3,046,134; Carroll et al. U.S. Pat.No. 2,944,900; and Goffe U.S. Pat. No. 3,294,540.

Likewise, the silver halide emulsions can be protected against theproduction of fog and can be stabilized against loss of sensitivityduring keeping. Suitable antifoggants and stabilizers each used alone orin combination include thiazolium salts described in Brooker et al. U.S.Pat. No. 2,131,038 and Allen et a1. U.S. Pat. No. 2,694,716; theazaindenes described in Piper U.S. Pat. No. 2,886,437 and Heimbach etal. U.S. Pat. No. 2,444,605; the mercury salts as described in Allen etal. U.S. Pat. No. 2,728,663; the urazoles described in Anderson et al.U.S. Pat. No. 3,287,135; the sulfocatechols described in Kennard et al.U.S. Pat. No. 3,236,652; the oximes described in Carroll et al. BritishPat. No. 623,448; nitron; nitroindazoles; the mercaptotetrazolesdescribed in Kendall et al. U.S. Pat. No. 2,403,927; Kennard et al. U.S.Pat. No. 3,266,897 and Luckey et al. U.S. Pat. No. 3,397,987; thepolyvalent metal salts described in Jones U.S. Pat. No. 2,839,405; thethiuronium salts described in Herz et al. U.S. Pat. No. 3,220,839; thepalladium, platinum and gold salts described in Trivelli et al. U.S.Pat. No. 2,566,263 and Yutzy et al. US. Pat. No. 2,597,915.

Any material can be employed as the image-receiving layer in thisinvention as long as the described function of mordanting or otherwisefixing the dye images will be obtained. The particular material chosenwill, of course, depend upon the dye image to be mordanted. 1f acid dyesare to be mordanted, the image-receiving layer can contain basicmordants such as polymers of amino guanidine derivatives of vinyl methylketone such as described in the Minsk U.S. Pat. No. 2,882,156 grantedApr. 14, 1959. Other mordants useful in the present invention includethe 2-vinyl pyridine polymer metho-ptoluene sulfonate and similarcompounds described in Sprague et a1. U.S. Pat. No. 2,484,430 grantedOct. 1 1, 1949, and cetyl trimethylammonium bromide, etc. Effectivemordanting compositions are also described in Whitmore U.S. Pat. No.3,271,148 and Bush U.S. Pat. No. 3,271,147. Furthermore, theimage-receiving layer can be sufficient by itself to mordant the due asin the case of use of an alkaline solution-permeable polymeric layersuch as N-methoxymethyl polyhexylmethylene adipamide; partiallyhydrolyzed polyvinyl acetate; polyvinyl alcohol with or withoutplasticizers; cellulose acetate; gelatin; and other materials of asimilar nature.

Polyvinyl alcohol or gelatin containing a dye mordant such aspoly-4-vinyl-pyridine as disclosed in U.S. Pat. No. 3,148,061 can alsobe employed in the invention for mordanting dye developers. Generally,good results are obtained when the image-receiving layer is from about0.25 to about 0.04 mil in thickness. This thickness, of course, may bemodified depending upon the result desired. The image-receiving layermay also contain ultraviolet absorbing materials to protect themordanted dye images from fading due to ultraviolet light.

Use of a polymeric acid layer, as disclosed in U.S. Pat. No. 3,362,819,in the film unit of the invention will enhance the results obtained.Generally, the polymeric acid layer will effeet a reduction in the pH ofthe image layer from about 13 or 14 to at least 1 1 and preferably 8within a short time after inhibition. Such polymeric acids reduce the pHof the film unit after development to terminate further dye transfer andthus stabilize the dye image. Such polymeric acids comprise polymerscontaining acid groups, such as carboxylic acid and sulfonic acidgroups, which are capable of forming salts with alkali metals, such assodium or potassium or with organic bases particularly quaternaryammonium bases. such as tetramethyl ammonium hydroxide. The polymers canalso contain potentially acid-yielding groups such as anhydrides orlactones or other groups which are capable of reacting with bases tocapture and retain them. Generally the most useful polymeric acidscontain free carboxyl groups, being insoluble in water in the free acidform and which form water-soluble sodium and/or potassium salts.

The polymeric acid layer is usually about 0.3 to about 1.5 mils inthickness. Although the polymeric acid layer is usually located in thereceiver portion of the film unit between the support and theimage-receiving layer, it can also be located in the negative portion ofthe film unit, as disclosed in U.S. Pat. No. 3,362,821.

An inert timing or spacer layer coated over the polymeric acid layer mayalso be used to "time" or control the pH reduction of the film unit as afunction of the rate at which the alkali diffuses through the inertspacer layer. Examples of such timing layers include gelatin, polyvinylalcohol or any of these disclosed in U.S. Pat. No. 3,455,686. The timinglayer is also effective in evening out the various reaction rates over awide range of temperatures, e.g., premature pl-l reduction is preventedwhen imbibition is effected at temperatures above room temperature, forexample, at 95 to 100 F. The timing layer is usually about 0.1 to about0.7 mil in thickness.

The photographic elements used with this invention can containantistatic or conducting layers, such layers may comprise soluble salts,e.g., chlorides, nitrates, etc., evaporated metal layers, ionic polymerssuch as those described in Minsk U.S. Pat. No. 2,861,056 and Sterman eta1. U.S. Pat. No. 3,206,312 or insoluble inorganic salts such as thosedescribed in Trevoy U.S. Pat. No, 3,428,451.

The liquid-processing composition employed in this invention is theconventional aqueous solution of an alkaline material, e.g., sodiumhydroxide, sodium carbonate or an amine such as diethylamine, preferablypossessing a pH in excess of 12. The composition also preferablycontains a viscosity-increasing compound such as a high molecular weightpolymer, e.g., a water-soluble ether inert to alkaline solutions such ashydroxyethyl cellulose or alkali metal salts of carboxymethyl cellulosesuch as sodium carboxymethyl cellulose. A concentration ofviscosity-increasing compound of about 1 to about 5 percent by weight ofthe processing composition is preferred which will impart thereto aviscosity of about 100 c.p.s. to about 200,000 c.p.s.

The layers of the photographic element employed and described herein canbe coated on a wide variety of supports. Typical supports includecellulose nitrate film, cellulose ester film, poly(vinyl acetal) film,polystyrene film, poly(ethylene terephthalate) film, polycarbonate filmand related films or resinous materials, as well as glass, paper, metaland the like. Typically, a flexible support is employed, especially apaper support, which can be partially acetylated or coated with barytaand/or an alpha-olefin polymer, particularly a polymer of analpha-olefin containing 2-10 carbon atoms such as polyethylene,polypropylene, ethylene-butane copolymers and the like.

The photographic elements of this invention can contain incorporateddeveloping agents such as hydroquinones, catechols, aminophenols,3-pyrazo1idones, ascorbic acid and its derivatives, reductones andphenylenediamines. Combinations of developing agents can be employed inthe practice of the invention. The developing agents can be in a silverhalide emulsion and/or in another suitable location the photographicelement. Especially useful auxiliary developing agents are colorlesshydroquinone derivatives such as those listed in column 6 of U.S. Pat.No. 3,253,915 of Weyerts et a1. issued May 31, 1966.

The photographic emulsions and elements described in the practice ofthis invention can contain various colloids alone or in combination asvehicles, binding agents and various layers. Suitable hydrophilicmaterials include both naturally occurring substances such as proteins,for example, gelatin, gelatin derivatives, cellulose derivatives,polysaccharides such as dextran, gum arabic and the like; and syntheticpolymeric substances such as water-soluble polyvinyl compounds likepoly(vinylpyrrolidone acrylamide polymers and the like.

The described photographic emulsion layers and other layers of aphotographic element employed in the practice of this invention can alsocontain alone or in combination with hydrophilic, water-permeablecolloids, other synthetic polymeric compounds such as dispersed vinylcompounds such as in latex form and particularly those which increasethe dimensional stability of the photographic materials. Suitablesynthetic polymers include those described, for example, in Nottorf U.SvPat. No. 3,142,568, issued July 28, 1964; White U.S. Pat. No. 3,193,386,issued July 6,1965;Houck et a1. U.S. Pat. No. 3,062,674, issued Nov. 6,1962; Houck et al. US Pat. No. 3,220,844 issued Nov. 30, 1965; Ream etal. US. Pat. No. 3,287,289, issued Nov. 22, 1966; and Dykstra U.S. Pat.No. 3,411,911, issued Nov. 19, 1968. Particularly effective are thosewater-insoluble polymers of alkyl acrylates and methacrylates, acrylicacid, sulfoalkyl acrylates or methacrylates, those which havecross-linking sites which facilitate hardening or curing and thosehaving recurring sulfobetaine units as described in Dykstra CanadianPat. No. 744,054.

The various photographic layers may contain plasticizers and lubricantssuch as polyalcohols, e.g., glycerin and diols of the type described inMilton et al, U.S. Pat. No. 2,960,404; fatty acids or esters such asthose described in Robijns U.S. Pat. No. 2,588,765 and Duane US. Pat.No. 3,121,060; and silicone resins such as those described in DuPontBritish Pat. No. 955,061.

The photographic layers used in the practice of this invention may becoated by various coating procedures including dip coating, air knifecoating, curtain coating, or extrusion coating using hoppers of the typedescribed in Belguin U.S. Pat. No. 2,681,294. If desired, two or morelayers may be coated simultaneously by the procedures described inRussell U.S. Pat, No. 2,761,791 and Wynn British Pat. No. 837,095. Thisinvention also can be used for silver halide layers coated by vacuumevaporation as described in British Pat. No, 968,453 and LuValle et a1.U.S. Pat. No. 3,219,451.

The photographic and other hardenable layers used in the practice ofthis invention can be hardened by various organic or inorganichardeners, alone or in combination, such as the aldehydes, and blockedaldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonateesters sulfonyl halides and vinyl sulfonyl ethers, active halogencompounds, epoxy compounds, aziridines, active olefins, isocyanates,carbodiimides, mixed function hardeners and polymeric hardeners such asoxidized polysaccharides like dialdehyde starch and oxyguargum and thelike.

The following nonlimiting example illustrates processes and productswithin the scope of the present invention:

EXAMPLE A photosensitive element is prepared by coating a subbed filmsupport comprising cellulose acetate with suitably hardened gelatinlayers sequentially coated as follows:

1. Cyan Dye Developer Layer The cyan dye developer5,8-dihydroxy-l,4-bis[(fihydroquinonyl-a-methyl)ethylamino]anthraquinoneis dissolved in a mixture of N-n-butylacetanilide and 4-methylcyclohexanone and dispersed in an aqueous gelatin solution with a sodiumdiisopropylnaphthalene sulfonate dispersing agent. The mixture is passedthrough a colloid mill several times, coated on the subbed support anddried so as to volatilize the 4-methyl cyclohexanone.

2. Red-Sensitive Emulsion Layer A gelatino silver bromoiodide emulsionlayer, which is sensitized to the red region of the spectrum, is coatedupon the cyan dye developer layer.

3. Interlayer A gelatin interlayer is then coated on the red-sensitiveemulsion layer. 4. Magenta Dye Developer Layer The magenta dye developer2 [p-(2',5'-dihydroxyphenethyl)-phenylazo]-4-n-propoxy-l-naphthol isdissolved in a mixture of cyclohexanone and N-n-butylacetanilide anddispersed in an aqueous gelatin solution with a sodium alkylnaphthalenesulfonate dispersing agent. The mixture is passed through a colloid millseveral times, coated on the interlayer and dried to volatilize thecyclohexanone. 5. Green-Sensitive Emulsion Layer A green-sensitivesilver-bromoiodide emulsion is coated on the magenta dye developerlayer. 6. lnterlayer A second gelatin interlayer is coated onto thegreen-sensitive emulsion layer. 7. Yellow Dye Developer Layer The yellowdye developer,l-phenyl-3-N-n-hexylcarboxamido-4-[p-(2',5-dihydroxyphenethyl)-phenylazo]-5-pyrazolone is dissolved in a mixture of ditetrahydrofurfuryl adipate andethylene glycol monobenzyl ether and dispersed in an aqueous gelatinsolution with a sodium diisopropylnaphthalene sulfonate dispersingagent. The mixture is passed through a colloid mill several times. Theresulting dispersion is chilled to set it, washed to remove ethyleneglycol monobenzyl ether followed by coating upon the second interlayerand dryin 8. Blue-Sensitive Emulsion Layer A blue-sensitive silverbromoiodide emulsion is coated onto the yellow dye developer layer. 9.Overcoat Layer A final gelatin overcoat layer is provided on theforegoing layers having dispersed therein an auxiliary developing agent4-methylphenylhydroquinone.

Samples of the photosensitive element are exposed for 1/50 sec. on anEastman 1b Sensitometer with a 500 w. tungsten light source throughappropriately filtered step tables as shown in Table 111. Next, one ofthe samples is processed with a stock processing solution having thecomposition set forth in Table 1 below:

The stock activator is spread between the negative and a receivingsheet. The exposed film is processed at a gap of 0.004 inch between apair of pressure rollers in order to spread the activator. The receivingsheet is a cellulose acetate butyrate subbed paper support carrying inthe following order:

1. a polymeric acid layer for pH control,

2. a polyvinyl alcohol spacer layer,

3. a mordant layer comprising poly-4-vinyl pyridine and polyvinylalcohol, and

4. a polyvinyl alcohol protective layer. After an inhibition period ofapproximately 1 minute, the receiver is separated from the negative andcontains a positive trichrome image of the photographed subject. Theforegoing procedure is repeated employing activators comprising thestock processing solution of Table 1 containing the added in- Theintegral red, green and blue densities of all the resulting transferimages are then measured by reflectance through red, green and bluefilters, respectively. Theoretically, only cyan dye developer shouldtransfer from the negatives exposed to green and blue light, onlymagenta dye developer should transfer from the negatives exposed to redand blue light, and only yellow dye developer should transfer from thenegatives that are exposed to green and red light. Since reflecteddensity of a particular color is being measured through a filter of thesame color, the lower the value means that more of that light is beingreflected. The results are set forth in Table 111 as follows:

TABLE III.REFLECTED PRINT DENSITY Exposure (Wratten filters) Max.density in Green and blue Blue and red Green and red unexposed area(W-44A) (two W-32) W-15 and W-25 Activator R G B R G B R G B R G B Stock1 35 2. 87 2. 52 1. 03 1. 71 1. 35 0. 66 1. 64 1. 31 42 0. 99 1. 15 A 0.87 1. 30 1. 62 0. 45 0. 46 0. 57 0. 24 0. 56 0. 59 19 0. 45 0. 84 B 1.512.97 2.58 1.39 1.96 1.69 1.01 1.97 1 68 .86 1.26 1.69 C 1. 26 1. 58 1.86 1. 25 0. 73 0. 82 0. 51 1. 12 0 89 30 0. 51 1. 29

Neutral Red Green Blue (unfiltered) (W-29) (W-99) (W-47B) Activator R GB R G B R G B R G B The foregoing results illustrate that Activator C.which contains the S-pyrazolone unsubstituted in the 4-position incombination with the onium compound. viz. l-phenethyl pyridiniumbromide. yields a print having decidedly more color separation than theprint made with the Activator A. which contains an onium compound havingno reactive methyl group (l-phenethyl pyridinium bromide). alone. lnaddition. the print produced with Activator C has acceptable D... andrum- The photographic layers employed in the practice of this in ventioncan contain surfactants such as saponin'. anionic compounds such as thealkyl aryl sulfonates described in Baldsiefen US. Pat. No. 2.600.831;amphoteric compounds such as those described in Ben-Ezra US. Pat. No.3.133.816. and water-soluble adducts of glycidol and an alkyl phenolsuch as those described in Olin Mathieson British Pat. No. 1,022,878. Inaddition. the photographic elements may contain matting agents such asstarch. titanium dioxide. zinc oxide, silica, polymeric beads includingbeads of the type described in Jelley et alv US. Pat. No. 2,992,101 andLynn US. Pat. No. 2,701,245.

The emulsions used in this invention can be sensitized with chemicalsensitizers. such as with reducing agents; sulfur. selenium or telluriumcompounds; gold. platinum or palladium compounds; or combination ofthese. Suitable procedures are described in Sheppard et al. US. Pat. No.l,623,499; Waller et al. US Pat. No. 2,399,083; McVeigh US Pat. No.3,297,477; and Dunn US. Pat. No. 3,297,466.

Spectral sensitizing dyes can be used conveniently to confer additionalsensitivity to the light-sensitive silver halide emulsion of themultilayer photographic elements of the invention. For instance,additional spectral sensitization can be obtained by treating theemulsion with a solution of a sensitizing dye in an organic solvent orthe dye may be added in the form of a dispersion as described in Owenset al. British Pat. No. 1,154,781. For optimum results, the dye mayeither be added to the emulsion as a final step or at some earlierstage.

Sensitizing dyes useful in sensitizing such emulsions are described, forexample. in Brooker et al. US. Pat. No. 2,526,632, issued Oct. 24, 1950;Sprague US. Pat. No. 2,503,776, issued Apr. ll, 1950; Brooker et al. USPat. No. 2,493,748; and Taber et al. US. Pat. No. 3,384,486. Spectralsensitizers which can be used include the cyanines, merocyanines,complex (tri or tetranuclear) merocyanines, complex (tri ortetranuclear) cyanines. holopolar cyanines, styryls, hemicyanines (e.g.,enamine hemicyanines). oxonols and hemioxonols. Dyes of the cyanineclasses may contain such basic nuclei as the thiazolines, oxazolines,pyrrolines. pyridines, oxazoles, thiazoles, selenazoles and imidazoles.Such nuclei may contain alkyl. aikylene, hydroxyalkyi, sulfoalkyl,carboxyalkyl, aminoalkyl and enamine groups and may be fused tocarbocyclic or heterocyclic ring systems either unsubstituted orsubstituted with halogen, phenyl, alkyl. haloalkyl, cyano, or allcoxygroups. The dyes may be symmetrical or unsymmetrical and may containalkyl. phenyl, enamine or heterocyclic substituents on the methine orpolymethine chain. The merocyanine dyes can contain the basic nucleimentioned above as well as acid nuclei such as thiohydantoins,rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids,thiasolineones, and malononitrile. These acid nuclei may be substitutedwith alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl,alkoxyalkyl, alkylamino groups, or heterocyclic nuclei. Combinations ofthese dyes may be used, if desired. In addition, supersensitizingaddenda which do not absorb visible light may be included, for instance,ascorbic acid derivatives, azaindenes, cadmium salts, and organicsulfonic acids as described in McFall et al. US. Pat. No. 2,933,390 andJones et al. US. Pat. No. 2,937,089.

The various layers, including the photographic layers, employed in thepractice of this invention can contain light-absorbing materials andfilter dyes such as those described in Sawdey US. Pat. No. 3,253,921;Gaspar US. Pat. No. 2,274,782; Silverstein et al. US. Pat. No. 2,527,583and Van- Campen U.S. Pat. No. 2,956,879. If desired, the dyes can bemordanted. for example. as described in Jones et al. US Pat. No.3.282.699.

The photographic elements used in this invention may contain brighteningagents including stilbenes, triazines. oxazoles and coumarin brighteningagents. Water-soluble brightening agents may be used such as thosedescribed in Albers et al. German Pat. No. 972.067 and Mel-all et al.U.5. Pat. No. 2.933.390 or dispersions of brighteners may be used suchas those described in Jansen German Pat. No. l.l50.274, Oetiker et al.US. Pat. No. 3,406,070 and Heidke French Pat. No. 1,530,244.

The sensitizing dyes and other addenda used in the practice of thisinvention can be added from water solutions or suitable organic solventsolutions may be used. The compounds can be added using variousprocedures including those described in Collins et al. US. Pat. No.2.912.343; McCrossen et al. U.S. Pat. No. 3,342,605; Audran US Pat. No.2.996.287 and Johnson et al. US Pat. No. 3,425,835.

While the invention has been described with reference to layers ofsilver halide emulsions and dye image-providing materials, dotwisecoating, such as would be obtained using a gravure printing technique.could also be employed. In this technique. small dots of blue, green andred-sensitive emulsions have associated therewith. respectively. dots ofyellow. magenta and cyan color-providing substances. After develop ment.the transferred dyes would tend to fuse together into a continuous tone.

The invention has been described with particular reference to certainpreferred embodiments thereof, but it will be understood that variationsand modifications can be efi'ected within the spirit and scope of theinvention.

lclaim:

1. A photographic film unit which is adapted to be processed by passingsaid unit between a pair of juxtaposed pressure-applying memberscomprising:

a. a photosensitive element comprising a support coated with at leastone photosensitive silver halide emulsion layer, each said silver halideemulsion layer having associated therewith a dye developer;

b. a dye image-receiving layer; and

c. a rupturable container containing an alkaline processing composition;

said film unit containing a 5 pyrazolone unsubstituted in the 4-position and an onium compound comprising a quaternary ammonium,quaternary phosphonium or tertiary sulfonium compound; said rupturablecontainer being adapted to be positioned during processing of said filmunit so that a compressive force applied to said container by saidpressure-applying members will effect a discharge of the containerscontents within said film unit.

2. The film unit of claim 1 wherein said dye image-receiving layer islocated in said photosensitive element between said support and thelowermost photosensitive silver halide emulsion layer.

3. The film unit of claim 1 wherein said dye image-receiving layer iscoated on a separate support and is adapted to be superposed on saidphotosensitive element after exposure thereof.

4. The film unit of claim 3 wherein said rupturable container is sopositioned during processing of said film unit that a compressive forceapplied to said container by said pressureapplying members will effect adischarge of the container's contents between said dye image-receivinglayer and the outermost layer of said photosensitive element. halide 5.The film unit of claim 4 wherein said photosensitive element comprises asupport coated with a cyan dye developer layer, a red-sensitive silverhalide emulsion layer, a magenta dye developer layer, a green-sensitivesilver halide emulsion layer. a yellow dye developer layer and ablue-sensitive silver halide emulsion layer.

6. The film unit of claim 5 wherein said S-pyrazolone unsubstituted inthe 4-position and said onium compound are provided in said rupturablecontainer.

7. The film unit of claim 6 wherein said onium compound possesses noactive methyl group.

8. The film unit of claim 7 wherein said onium compound is a quaternaryammonium compound.

9. The film unit of claim 8 wherein said quaternary ammonium compound isl-phenethyl pyridinium bromide, l-ethyl pyridinium bromide,l-phenethyl-3-picolinium bromide, or 1- n-nonylpyridiniump-toluenesulfonate.

10. The film unit of claim 9 wherein said S-pyrazolone unsubstituted inthe 4-position is l-phenyl-3-methyl-5- pyrazolone.

11, A photographic film unit which is adapted to be processed by passingsaid unit between a pair of juxtaposed pressure-applying memberscomprising:

a. a photosensitive element comprising a support coated with a cyan dyedeveloper layer, a red-sensitive silver halide emulsion layer, a magentadye developer layer, a green-sensitive silver halide emulsion layer, ayellow dye developer layer, and a blue-sensitive silver halide emul sionlayer;

b. a dye image-receiving layer coated on a support and adapted to besuperposed over said blue-sensitive silver halide emulsion layer afterexposure of said photosensitive element; and

c. a rupturable container containing an alkaline processing compositionwhich is adapted to be positioned during processing of said film unit sothat a compressive force applied to said container by saidpressure-applying members will effect a discharge of the container'scontents between said dye image-receiving layer and said blue-sensitivesilver halide emulsion layer of said photosensitive element, saidrupturable container additionally containing a S-pyrazoloneunsubstituted in the 4-position in an amount of from about 1 to about 4percent by weight of said processing composition and an onium compoundhaving no reactive methyl group in an amount of from about 1 to about 10percent by weight of said processing composition.

12. A process for producing a photographic transfer image in colorcomprising:

a. imagewise exposing a photosensitive element comprising a supportcoated with at least one photosensitive silver halide emulsion layer,each silver halide emulsion layer having associated therewith a dyedeveloper;

b. treating said photosensitive element with an alkaline processingcomposition;

c. effecting development of each of said exposed silver halide emulsionlayers;

d. forming an imagewise distribution of diffusible dye developer as afunction of said imagewise exposure of each of said silver halideemulsion layers; and

e. at least a portion of each of said imagewise distributions ofdiffusible dye developer diffusing to a dye imagereceiving layer;

said development being effected in the presence of a 5- pyrazoloneunsubstituted in the 4-position and an onium compound comprising aquaternary ammonium, quaternary phosphonium or tertiary sulfoniumcompound.

13. The process of claim 12 wherein said treatment step (b) is effectedby:

a. superposing over the layer outermost from the support of saidphotosensitive element said dye image-receiving layer coated on asupport;

b. positioning a rupturable container containing said alkalineprocessing composition between said exposed photosensitive element andsaid dye image-receiving layer; and

c. applying a compressive force to said container to effect a dischargeof the containers contents between said outermost layer of said exposedphotosensitive element and said dye image-receiving layer.

14. The process of claim 13 wherein said onium compound possesses noreactive methyl group.

15. The process of claim 14 wherein said onium compound is a quaternaryammonium compound.

16. The process of claim 15 wherein said quaternary ammonium compound isl-phenethyl pyridinium bromide, lethyl pyridinium bromide,l-phenethyl-3-picolinium bromide, or l-n-nonylpyridiniump-toluenesulfonate.

17. The process of claim 16 wherein said S-pyrazolone unsubstituted inthe 4-position is l-phenyl-3-methyl-5- pyrazolone.

18. The film unit of claim 5 wherein the photosensitive element containsan auxiliary developing agent.

2. The film unit of claim 1 wherein said dye image-receiving layer islocated in said photosensitive element between said support and thelowermost photosensitive silver halide emulsioN layer.
 3. The film unitof claim 1 wherein said dye image-receiving layer is coated on aseparate support and is adapted to be superposed on said photosensitiveelement after exposure thereof.
 4. The film unit of claim 3 wherein saidrupturable container is so positioned during processing of said filmunit that a compressive force applied to said container by saidpressure-applying members will effect a discharge of the container''scontents between said dye image-receiving layer and the outermost layerof said photosensitive element.
 5. The film unit of claim 4 wherein saidphotosensitive element comprises a support coated with a cyan dyedeveloper layer, a red-sensitive silver halide emulsion layer, a magentadye developer layer, a green-sensitive silver halide emulsion layer, ayellow dye developer layer and a blue-sensitive silver halide emulsionlayer.
 6. The film unit of claim 5 wherein said 5-pyrazoloneunsubstituted in the 4-position and said onium compound are provided insaid rupturable container.
 7. The film unit of claim 6 wherein saidonium compound possesses no active methyl group.
 8. The film unit ofclaim 7 wherein said onium compound is a quaternary ammonium compound.9. The film unit of claim 8 wherein said quaternary ammonium compound is1-phenethyl pyridinium bromide, 1-ethyl pyridinium bromide,1-phenethyl-3-picolinium bromide, or 1-n-nonylpyridiniump-toluenesulfonate.
 10. The film unit of claim 9 wherein said5-pyrazolone unsubstituted in the 4-position is1-phenyl-3-methyl-5-pyrazolone.
 11. A photographic film unit which isadapted to be processed by passing said unit between a pair ofjuxtaposed pressure-applying members comprising: a. a photosensitiveelement comprising a support coated with a cyan dye developer layer, ared-sensitive silver halide emulsion layer, a magenta dye developerlayer, a green-sensitive silver halide emulsion layer, a yellow dyedeveloper layer, and a blue-sensitive silver halide emulsion layer; b. adye image-receiving layer coated on a support and adapted to besuperposed over said blue-sensitive silver halide emulsion layer afterexposure of said photosensitive element; and c. a rupturable containercontaining an alkaline processing composition which is adapted to bepositioned during processing of said film unit so that a compressiveforce applied to said container by said pressure-applying members willeffect a discharge of the container''s contents between said dyeimage-receiving layer and said blue-sensitive silver halide emulsionlayer of said photosensitive element, said rupturable containeradditionally containing a 5-pyrazolone unsubstituted in the 4-positionin an amount of from about 1 to about 4 percent by weight of saidprocessing composition and an onium compound having no reactive methylgroup in an amount of from about 1 to about 10 percent by weight of saidprocessing composition.
 12. A process for producing a photographictransfer image in color comprising: a. imagewise exposing aphotosensitive element comprising a support coated with at least onephotosensitive silver halide emulsion layer, each silver halide emulsionlayer having associated therewith a dye developer; b. treating saidphotosensitive element with an alkaline processing composition; c.effecting development of each of said exposed silver halide emulsionlayers; d. forming an imagewise distribution of diffusible dye developeras a function of said imagewise exposure of each of said silver halideemulsion layers; and e. at least a portion of each of said imagewisedistributions of diffusible dye developer diffusing to a dyeimage-receiving layer; said development being effected in the presenceof a 5-pyrazolone unsubstituted in the 4-position and an onium compoundcomprising a quaternary ammonium, quaternary phosphonium or tertiarysulfonium cOmpound.
 13. The process of claim 12 wherein said treatmentstep (b) is effected by: a. superposing over the layer outermost fromthe support of said photosensitive element said dye image-receivinglayer coated on a support; b. positioning a rupturable containercontaining said alkaline processing composition between said exposedphotosensitive element and said dye image-receiving layer; and c.applying a compressive force to said container to effect a discharge ofthe container''s contents between said outermost layer of said exposedphotosensitive element and said dye image-receiving layer.
 14. Theprocess of claim 13 wherein said onium compound possesses no reactivemethyl group.
 15. The process of claim 14 wherein said onium compound isa quaternary ammonium compound.
 16. The process of claim 15 wherein saidquaternary ammonium compound is 1-phenethyl pyridinium bromide, 1-ethylpyridinium bromide, 1-phenethyl-3-picolinium bromide, or1-n-nonylpyridinium p-toluenesulfonate.
 17. The process of claim 16wherein said 5-pyrazolone unsubstituted in the 4-position is1-phenyl-3-methyl-5-pyrazolone.
 18. The film unit of claim 5 wherein thephotosensitive element contains an auxiliary developing agent.